This invention relates to electrical panelboards which incorporate an internal electrical subassembly of various devices, such as circuit breakers or fuses and an enclosure. More particularly, the invention relates to a panelboard equipped with concealed clamps for attaching the front or trim to a wall-mounted sheet metal box or the like.
In the prior art, a variety of different means were used for fastening a "trim" or front onto wall-mounted panel assemblies. These panels usually include a sheet metal box which is mounted in a wall so as to be recessed from the front surface of the wall or to be flush with the surface of the wall. A panelboard front or "trim," together with a suitable door, is provided for completing the enclosure of the panel assembly and allows access to the control elements of the circuit devices through an opening in the front that is normally covered by the door.
Such panelboard fronts should be easily attached and removed from position, preferably by one person, for access to the devices and terminals of the panel when necessary. It is desirable that the means which attaches the panelboard front or trim to the panel assembly be concealed when the door of the assembly is closed and locked to prevent unauthorized access to the interior. It is also desirable that the means for fastening the panelboard front to the assembly be adjustable or otherwise adapted to engaging panelboard boxes which are recessed from the front surface of the wall at different depths or in irregular fashion, whether canted laterally or unaligned vertically with the surface of the wall. Stated another way, the attachment means for the panelboard front should be adjustable to assure that the trim will be flush with the wall when it is secured in place, both for satisfactory appearance and for rendering the panel tamper proof for maximum security in corridors and other wall areas exposed to public traffic.
It is known to attach panelboard fronts to a panel box by means that is covered by the door when it is closed. An example is Wills, U.S. Pat. No. 2,871,284, in which the front is attached to the panel box by sufficiently long screws which are screwed into an arm on a bracket that is attached to the rear of the box. Various other techniques involving the use of relatively complicated clamping mechanisms have been developed in which the manipulative elements thereof are covered by the door when closed. Such clamps usually include two or more members pivoted together so that one engages the trim and another is disposed for engaging the flange of the box as a clamp. Such arrangements usually require a long threaded screw for providing sufficient adjustability for recessed panelboard boxes or a rotatable clamp member which can be rotated out of clamping position so that they will clear the flanges of the box when the panelboard front is initially placed in position, or when it is being removed.